1. Field of the Invention
Internal combustion gasoline engine design is undergoing important changes to meet stricter standards set for engine and exhaust gas emissions. One major change in engine design is the feeding of blow-by gases from the crankcase zone of the engine into the intake air-fuel mixture at the carburetor just below the throttle plate, rather than venting these gases to the atmosphere as was the practice formerly. These blow-by gases contain substantial amounts of deposit forming substances and are known to form deposits in and around the throttle plate area of the carburetor. Another significant change in engine design and operation is the recirculation of a part of the exhaust gases to the fuel air intake of the engine. These exhaust gases also have pronounced deposit forming tendencies. The carburetor deposits produced by the recirculated blow-by and exhaust gases restrict the flow of air through the carburetor at idle and at low speeds so that an overrich fuel mixture results. This condition produces rough engine idling and/or stalling and leads to the release of excessive hydrocarbon exhaust emissions to the atmosphere.
Many detergent additives for motor fuel compositions are known in the art and are eminently effective for this purpose. There is, however, a major drawback associated with the use of many of the known carburetor detergents including materials which are outstanding carburetor detergents. The problem referred to is the octane requirement increase of the engine brought about as a result of the use of the carburetor detergent. While not fully understood, many carburetor detergents cause an octane requirement increase in the engine of 3 or 4 or more octane units as measured by the Research Octane Number method. This phenomenon is believed to be due to an increase in deposits formation in the combustion zone of the engine leading to a higher than design compression ratio in the engine and a higher octane requirement. This is a very serious problem when viewed from its impact on the comsumption of high octane gasoline with its reduced volumetric yield from the basic petroleum resource.
The detergent additive is also useful in diesel oils, fuel oils, engine oils and in mineral lubricating oil compositions.
2. The Prior Art
Detergent oil compositions are disclosed in U.S. Pat. Nos. 3,275,554; 3,676,089; 3,905,781 and 3,927,104.
A copending application Ser. No. 753,962 filed Dec. 23, 1976, now abandoned in favor of a continuation, Ser. No. 940,928, filed Sept. 11, 1978 is directed to the additive reaction product of a hydrocarbylsuccinic anhydride in which the hydrocarbyl radical has from about 6 to 30 carbon atoms and to rust-inhibited oil compositions containing the additive.